This invention relates to placing an electric motor protection device on the non-orbiting scroll in a scroll compressor to stop operation of the motor should adverse conditions be detected.
Scroll compressors are widely utilized in modern refrigerant compression applications. In a scroll compressor, a pair of scroll members each include a base and a generally spiral wrap extending from the base. The wraps interfit to define compression chambers. One of the two members is caused to orbit relative to the other, and the size of the compression chambers is decreased. An entrapped refrigerant is compressed, and moves to a discharge port which extends through the base of one of the scroll members.
There are many challenges with the design of scroll compressors. In particular, scroll compressors are designed to orbit in only one direction. If the orbiting scroll is caused to orbit in a direction reverse from the design direction, then refrigerant is drawn into the discharge port and moved toward a suction port. This is undesirable, and can cause excessive heat around the scroll members.
Scroll compressors have been proposed with protection elements to address this reverse rotation, and other problems. In particular, the electric motor is often provided with a protector circuit. The protector circuit incorporates electronics which respond to excessive current or voltage, and excessive heat. Historically, the protector circuit is incorporated into the electric motor, and adjacent to the stator windings.
Protector circuits have been proposed which are placed within the refrigerant flow adjacent to the discharge port. These protector circuits are connected to the electric motor. Should the discharge refrigerant exceed a maximum temperature, the protector circuits will then stop operation of the motor.
However, reverse rotation does not necessarily affect the temperature of the discharge refrigerant. In reverse rotation, as mentioned above, the refrigerant is drawn into the discharge port. The discharge chamber refrigerant is not heated excessively. However, the compressor pump unit is heated excessively, and undesirably.
One other prior art system locates a portion of a motor sensor on the non-orbiting scroll. This sensor is then wired into series with the motor protection circuit on the motor. However, the sensor does sense the temperature of the refrigerant in the discharge port. Further, it is undesirable to have two separate protector circuits as the complexity and expense increases.
In one major cause for such reverse rotation, the windings of the three phase electrical motor are improperly connected such that the phases are reversed. In such a situation, it is desirable for the protector circuit to quickly stop operation of the motor. The earliest, and most reliable indication of reverse rotation is excessive heat at the pump unit. The prior art protector circuits are not designed to respond to such feedback.
In a disclosed embodiment of this invention, a motor protector circuit is connected into the electric motor circuit for a scroll compressor. The protector circuit may be as utilized in the prior art; however, it is preferably mounted on the base of the non-orbiting scroll. In this way, the protector circuit is operable to respond to temperatures in the compressor pump unit, and quickly stop operation of the motor should reverse rotation occur. The current and voltage are still sensed by the motor protection circuit. Thus, electrical anomalies which have typically tripped the motor protector circuit when mounted on the motor are still sensed by the inventive motor protector circuit, and the motor is still stopped should there be an excessive electrical quantity passing through the motor protector circuit.
Preferably, the motor protector circuit is sealed from the discharge pressure refrigerant. The motor protector circuit is preferably mounted into a recess in an outer face of the base of the non-orbiting scroll. In a first embodiment, a separator plate is utilized in conjunction with the non-orbiting scroll. The separator plate separates the compressor housing into discharge and suction pressure chambers. In this embodiment, a simple plastic coating electrically insulates the motor protector circuit from the surrounding environment.
In a second embodiment, the separator plate is eliminated. In this embodiment, the shell of the compressor is secured to the non-orbiting scroll, and a seal between the two is provided. In this embodiment, a plastic cover is again mounted to electrically insulate the protector circuit from the non-orbiting scroll. Further, a sealing cap seals the recess which receives the protector such that the protector is sealed from a discharge pressure chamber defined on one side of the non-orbiting scroll.
Stated another way, the motor protector is within the axial length of the compressor pump unit. In preferred embodiments, the motor protector is mounted on the base of the non-orbiting scroll. However, the motor protector could be mounted on the crankcase, or even on the inner periphery of the housing for the compressor.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.